Hi If the idea is to generate a rate card and keep it up to date ….. I think that can be done with just the GPS. The CSAC really does not add a lot that I can see to that case.
Of course I may have (yet again) missed something …. ====== The very standard / “old school” approach for this is a microphone on the case of the M21. These days feed the mic preamp output into a cheap micro along with the GPS info and away you go. Spit the results out to a little OLED display maybe ….. Bob > On Feb 1, 2020, at 1:39 PM, Tom Bales <[email protected]> wrote: > >> >> Many thanks for everyone's response on my cesium-synchronized mechanical >> chronometer project. I'll keep the group informed of progress. Some >> responses to your questions and suggestions: > > > - My current plan is to use a chronometer that has been adjusted for > rate and is close to dead-on. Of course, they're never dead-on, and that's > why keeping track of the rate is important. I haven't dismissed the idea > of actually disciplining the chrono from the CSAC, but since this chrono's > rate adjustment involves screws on the balance wheel (it has a free-sprung > helical balance spring without any means of adjustment), that would be a > great challenge. Perhaps the best would be for the CSAC system to maintain > a "rate card" of the chronometer, so that when all the electronics fail, > and the user is left with only the chrono, at least they would have a > really good knowledge of its rate and variation. Doing so would require a > feedback signal from the chrono, which could be acoustic or photoelectric. > The electronic rate card could be updated now and then by turning off the > sync impulse to the chrono and listening for the ticks to move relative to > the 1pps. > - The chrono would need a bigger box in order to incorporate the > CSAC/GPS system, microcontroller, and--the biggest part--backup batteries. > That's part of the fun, and I'm thinking to mount the gimballed chrono in a > purpose-built enclosure that will hold everything. Connections to the > chrono will have to be very flexible FFC or silicone wire. > - I thiink auto-winding is a definite requirement. The engineering > challenge is to couple a small gearmotor to the winding system without > disabling the manual-winding system that uses a ratcheted key. Winding > noise should be short in duration, so it probably won't affect the time > sync. People have wound chronos by turning them upside down in the gimbals > and poking a key through a hole for a long time without any big issues. > - Coupling to the chrono balance and escapement might be difficult, or > it might be easy. If it takes hours or days to synchronize, that's OK, I > think. My guess is that anything that generates a slight impulse in the > direction of the escapement detent or a torque pulse to couple to the > balance will work well enough--a tiny little linear or rotary > electromagnetic actuator should work. We'll see. > - The Hamilton M21 chrono beats at 2Hz, so driving it with a 1pps signal > will probably work fine. > - The idea that TVB suggests of disciplining the CSAC to match the > chrono is fascinating, indeed. Hadn't thought of that one. It would be > the easiest way to keep the chrono and CSAC in sync, and it would still use > the traditional rate-card method of keeping track of the actual time. > Hmmmm. > - Yes, the CSAC modules are expensive! Over $5k currently. It seems > like during the evaluation period the company sold them "at a discount" in > order to build applications and sales (or so the court documents say). Let > me know if anyone sees a gyneesium one on *bay. I thought long and hard > before buying it, but idle hands are the devil's cash register. (Oh, > oh!--now I have an excuse to buy an HP 53230!) In my initial measurements > of rate (after GPS disciplining for 24 hours) the CSAC freewheels within > 1.7ms/yr. Probably good enough. Needs longer testing. > - The M21 has a single balance wheel consisting of an Invar spoke and a > stainless steel ring (it was Hamilton's magical way of doing temperature > compensation to match the balance spring. The Russian knock-offs have a > standard bi-metal split balance wheel. The Hamiltons beat just about > anything in performance. Besides, "Murica!". > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
